All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
If you were eligible to receive this sports certificate but you could only get it by paying money to that man, then there is no harm on you in what you did. The sin falls on that man who took the money illegally from you. Your work as well as your earnings from it are lawful and there is no problem in it.
However, if you were not entitled to this certificate, then you are sinful for giving a bribe. You must repent to Allah from this.
As for your work and your earning from it, then if you are qualified for this job and you do it as required, then the job is lawful.
For more benefit, please refer to Fatwa 314146, 234943, 96435, 92048 and 385465.
Allah knows best.