Help! Getting married on Friday!

So I was laying in bed with my fiancé on Thursday night and he says I think I have a pimple on my penis, it hurts like a pimple that’s about to pop. He’s a bigger guy and works a physical job so he’s sweaty a lot. We looked and sure enough he does have a small little bump. I forgot about it and asked again last night if it was still there and he said yes.

Now he’s never given me any reason to think that he may have cheated, and he told me about this he didn’t try to hide it. Is it more than likely just a pimple ? Can you get just a pimple on your penis ? I should note my last Obgyn appointment was in February and he always runs everything and I was negative for everything. Any advice is appreciated!