Pain after vaccination

The woman who we got our puppy from, and friends recommended that we just purchase puppy shot #2 (and #3) from the local farm supply and do it ourselves. So we did #2, and now there is a soft lump and its sensitive to the touch... its been about 3 hours, when does it necessitate a vet visit. He is eating, playing, peeing and pooping normally. But the most gentle touch to the area and he squeals/yips. We've had puppies before but this is our first time self-vaccinating so Im extra nervous.