Hi
I d like to suggest that you get it checked with your GP & see whether he can refer you to a specialist & as youve said youre scared -make a request to see whether it can be treated as urgent
What you likely have is a bacterial infection, these are really common if you received oral without having a condom on.
Go visit a pharmacist and explain you have an oral infection on your penis and they will give you an appropriate medication, you could see your GP but they will prescribe the same medication