I would've and actually did call the vet when Lucy had the lump but also she kept messing with her staples and running around too much. They had to replace two staples, and then the lump showed up and gradually went away.
Well when she had her stitches out last night the vet looked & said that it wasn't just fluid build up, that it is a reaction to the internal stitches and that it could take as long as 6 months to go away. I'm not too worried because it does look better already.