Doctors? haha, he will still have his arm, don't play childish, Lucy. He only have a lump, some skin creme it will diminish it. Although yes, if it's your first injection that how a needle in an arm looks. That will not go away.
Just looks like a hematoma from nicking the side of the vessel going in or out - ice it a bit and rotate sites for awhile if you choose to continue using. If it gets hard or warm go to a doc.
As long as the swelling stays to a minimum it'll be okay I've had my hand swell really bad but within 3days all the swelling was gone that's my rule of thumb if the swelling isn't gone in 3 days you needa go to the doctor n get put on some antibiotics you don't want lose a limb
Here's an abcess that came about due to a missed shot
It took 6 months to heal and multiple rounds of antibiotics it's fully healed n I actually got sepsis from this abcess if you do get an abcess pay really close attention to your tempature as anything above 101 you should go to the hospital and tell them you have an abcess and a fever it's nothing to play around with you can die from an abcess