Nyorai kuenderera mberi kwechikamu chino - Niyonkuru's debut pamakwikwi epasi rose yaive pa2005 IAAF World Cross Country Championships
. Akakwikwidza mumakwikwi evarume vechidiki uye akapedza ari wechi33 pavatambi 133 munguva yemaminitsi 25 nemasekondi 32. Muna 2005 Jeux de la Francophonie Niyonkuru akakwikwidza mumakwikwi emamita zviuru gumi. Niyonkuru akapedza ari wechina nenguva yemaminitsi makumi maviri nemapfumbamwe nemasekondi gumi nemasere, masekondi 0.03 chete kumashure kwemukundi wesirivheri, Moroccan Abderrahim Goumri. Niyonkuru akabva akwikwidza mu2006 World Junior Championships. Akapedza ari wechishanu mumamita 10 000 munguva yemaminitsi 28 nemasekonzi 59,92. Akanga ari 6.63 seconds shure kwomukundi, Ibrahim Jeilan wokuEthiopia. Muna 2007, Niyonkuru akakwikwidza pa2007 World Cross Country Championships mumakwikwi evarume vechidiki. Akapedza ari wechi13 mumaminiti 24 nemasekonzi 56. Akapedza ari kumashure kwemasekonzi 49 kubva kune akahwina menduru yegoridhe, wekuKenya Asbel Kiprop. Pa2009 World Military Track and Field Championships, Niyonkuru akahwina menduru yesirivheri mumamita zviuru gumi. Nguva yake yemaminitsi 29 nemasekonzi 37.14 yaive 23.67 masekondi kumashure kwemukundi menduru yegoridhe, Essa Ismail Rashed weQatar. Niyonkuru akanga ari 4.97 masekondi pamberi pemukundi wemhangura, weTunisia El Akhdar Hachani. Niyonkuru akakunda 2015 Auray-Vannes Half Marathon munguva yeawa imwe, maminitsi matatu nemasekondi makumi maviri. Pa2016 Summer Olympics, Niyonkuru akakwikwidza mumakwikwi evarume emarathon musi wa21 Nyamavhuvhu 2016, asi haana kupedza nhangemutange. Muna 2017 akakwikwidza mumarathon evarume pa2017 World Championships muAthletics, achiisa 71st mu2:42:27.