The National League sold the Republic of Ireland midfielder to the Cherries for £175,000 in 2012 and had a 15% sell-on clause included in the deal.
O'Kane moved for an undisclosed fee, but Nicholson says any money will go to help the cash-strapped club.
"I don't think I'll be getting anything," Nicholson told BBC Devon.
"There's more important things."
The Gulls are still looking for new owners having been taken over by a consortium of local business people last summer.
They were forced to close down the club's academy and drastically reduce the playing budget after millionaire former owner Thea Bristow left the club.

Members of the NASUWT are staging a 24-hour stoppage after claiming their relationship with the trust running Whitehaven Academy has broken down.
Teachers who are members of the ATL and NUT are taking part in similar action on Friday.
The Bright Tribe Trust said it was working to tackle known issues.
The academy was hit by a strike by the NASUWT on 10 January.
The school, which caters for 620 pupils, was rated inadequate by Ofsted inspectors last October and placed in special measures after being told it must improve its leadership.
Unions said teachers had "serious concerns" about the way in which they were being managed and the working environment within the school.
Academy bosses said the industrial action was "disappointing" but added they were hopeful of further talks with unions.
The school said classes for Year 11 pupils would be held as normal over the two days of industrial action.

The team needed to finish in the top three to secure a spot at next year's Pyeongchang qualification tournament.
However, in the play-off in Japan they were comprehensively beaten 5-1 by Slovakia - a team they had only lost 1-0 to in Friday's final pool game.
Matt Clarkson grabbed a late consolation strike for GB.
GB had lost heavily to the Czech Republic and Japan in their first two pool games and those two countries will join Slovakia at next year's tournament, from which the top two finishers will qualify for the Games in South Korea.
GB were last represented in the sport at the Winter Paralympics in Turin, Italy in 2006, when double gold medal-winning sprinter Richard Whitehead was part of the squad.

Wisley Property Investments is hoping to build homes, shops, a school, health centre and sports pitch on the former Wisley Airfield site.
A decision was expected by 24 December but Guildford councillor Tony Rooth said more information was needed.
However, Guildford greenbelt councillor Susan Parker fears the delay will play into the developer's hands.
Ms Parker, leader of the Guildford Greenbelt Group, said the decision could be taken away from the borough if it doesn't come to a decision by the agreed date.
She explained: "The applicant could seek to go to the inspector on the grounds of non-determination which means the council hasn't decided therefore you have to decide Mr Inspector.
"And the inspector normally has more of the presumption in favour of approving something if there has been non-determination."
But Guildford's lead councillor on housing Tony Rooth said it was a very big project with "all sorts of issues" which would take a long time to evaluate.
He added:  "What we need are brownfield sites where much-needed housing in Guildford can be built.
"Whether Wisley qualifies as a brownfield, or even a white concrete site as opposed to a Greenbelt site, we will evaluate when the applications are fully ready to consider."
Guildford Borough Council confirmed the 24 December date was "now unlikely" and said it would be seeking to agree a further extension of time.
Torquay United boss Kevin Nicholson says none of the money from Eunan O'Kane's move to Leeds from Bournemouth will go to the playing squad.
[NEXT_CONCEPT]
A Cumbrian school has cancelled lessons for the majority of pupils after being hit by industrial action for the second time this month.
[NEXT_CONCEPT]
Great Britain's Para ice hockey team will miss the 2018 Winter Paralympics after losing their World Championship B Pool bronze medal play-off.
[NEXT_CONCEPT]
A decision on plans to build more than 2,000 homes on a former airfield in Surrey has been delayed.