I Masturbate Daily, And For A Long While Now (3-4

I masturbate daily, and for a long while now (3-4 months) I have noticed a dull pain in my groin area (upper thigh, both sides). No pain or tenderness in my genitals. I also feel hard, painless lumps beneath the skin in the area; these are small, and not numerous (3 on right, 5 on left). I do not feel pain during normal activity, only when swimming breaststroke. I don't get pain anytime else. I am not sure what the cause is. Any help is appreciated.