Yes it can be a common thing. Usually it results from either the sutures irritating the tissue around them or the dog haveing an allergic reaction to the suture material. If the vet used absorbable sutures inside the area where the fluid filled bump is, then it will take some time for the suture material to break down and be absorbed by the body. Once that happens the bump will go away but it usually takes 6-8 weeks for that to happen. If he used a suture that will not break down, then it may create a problem. I have only seen that happen once where the surgeon actually had to go back in and remove the suture and suture it with something else. That is very rare so it is more likely it is a reaction that will resolve itself in a few weeks.