Trigger,
If the mass was absorbed back into the body it was more than likely bruised tissue and blood as puss will not be absorbed. LA200 was my old choice of medicine but opted to go with Draxxin as it is a one shot med. in most cases and works great on puss abscess's.
One thing I do is check the abscess with a large needle/syringe 16 gage or 18 gage and draw back on it. If it is blood fluid it will be absorbed and antibiotic treatment is all that is needed. But if it is green toothpaste puss it will need to be drained. I forgot to mention this in above post.