knots in her stomach

i was cutting my dogs nail and i had her on her back when i noticed she had a knot under the skin next to one of her nipples down by her priavte area. y question is what could it be? also she is not fixed

[Dan Sims, DVM]

You could be feeling a mammary mass and a trip to your veterinarian is due.
Some mammary masses are benign and your vet will advise you on surgery if needed.