Little lumps are ok
Young babies don't have much leg muscle yet.
Sometimes after a shot, there will be a lump in the leg muscle for a few days to a couple of weeks. If the lump is big (more than 1 inch wide), seems to hurt a lot, is warm and reddened, or is causing the baby to fuss a lot, a return trip to the doctor for a re-check is recommended. Getting more than one shot in each leg may cause more symptoms.