Hey. I just wondered if your pea sized lump ever completely disappeared, or if you found out what it was exactly? I’m experiencing what sounds like the same thing, it’s even slightly on the left hand side too. I only noticed it after I had suspected food poisoning. When I noticed it, I have flared it up by keep on prodding it, and trying to see what it felt like through the skin. It’s now 4 days since noticing and it’s still there, so would be keen to know how yours turned out.
Always best to see a doc and get professional eyes on it. It 'could' be a lymphocele which is a hard lump that appears and although it usually happens after something traumatic like a surgical procedure, it can happen after sex. It's trauma related. Given you also have an injury in your nearby groin . . . perhaps. It also very well could be a cyst (normally harmless). I'd get it checked by a doctor if it is there at the end of this week.
I forgot to add, my left groin is strained from playing basketball.