Is there a small hole in it like a bug bite? Have you been in the woods or outdoors recently? Maybe it could be a bot fly? Or something as simple as an irritation or an ingrown hair. You should likely see a doctor before it gets worse.
Well my grandfather had a simular case, he had a small bump in his stomach side, he went to the the doctor to check it out, they took an obtopsy and it ended up being skin cancer. You should deff go get a check up.
my husband has this they told him it is an ingrowing hair,he has to have an opp to have it removed