Cracking in while grinding with my gf?

Well my gf was on top of me and we were grinding. Then i a sudden crackling feeling happened in my . I didn't really hurt much and i still could receive an afterwards. It's hurtin g alittle now in my testicles but that's about it. Could it just be a ligament cracking like when you crack you knuckles? It's not swollen or anything. Some answers would be great, thanks!