Hi , My Name Is Linda. I Am 7 Months

Hi , my name is Linda. I am 7 months post op liver transplant. I have had a few post op complications. Last one was a seroma. Very small & healed now. Today I noticed a new area on my incision on the left side that looks like a blister about the size of a dime. It is purplish around it. This left side of my incision always has been sore & dosen't look like the right side which is a normal scar & I never had dicomfort there. Can lay on that easily. Left side just a bit of discomfort but not bad. What could be causing this bubble area on the incision?