Marley has a small bump thing under his right arm, it's about the size of my pinkie nail (so like, a bit smaller than a dime). It doesn't seem to hurt him. He had a burst abcess a few weeks ago, by his genitals, and it healed up alright and there's no lump there. This doesn't feel like it's a part of the skin, it's something underneath I think. What else could it be? Any ideas?