Good call going to the docs. Better safe than sorry. Antibiotics must have felt so good to take; i've been there.
Delt injects can be wierd, I always stick to glutes and quads are rarely have an issue. I only pin delts when my glutes/quads are very sore. I've only pinned delts 4 times EVER. 2 went very well, the other two not so much. My first shot ever was a left delt, and 4-5 days later I had some RUGGED signs/symptoms:
1. Severe swelling all the way down about 5-6" past my elbow on the posterior side (along the ulna). Seemed like it was filled with water, very puffy and soft.
2. Deep dark redness from the delt, along the long head of the biceps and the lateral head of the triceps.
3. An even darker (black/blue) lump around the deltoid insertion at the deltoid tuberosity (halfway down my upper arm).
4. A rock hard injection site at the delt, which spread to the bis/tris.
5. Entire upper arm was hot to the touch.
6. A pretty bad fever, waking up at night really hot and sweaty yet shivering.
I went to the ER, and got some antis. Went away in a few days.
I didn't pin delts for another month or so. Then I manned up and pinned delts again, both sides, and everything went perfectly. Barely even any soreness. Feeling good about the delts, I tried it for the 4th time, this time on the right delt. The EXACT same symptoms as the first, SCARY STUFF.
This time I did NOT go to the docs, and it lasted just as long as before, but 3-4 days after these scary symptoms appeared, they were gone. Swelling went down, redness disappeared, no more fevers, lump shrunk and went away, etc.
I still wonder what the fuck happened during these two bad shots...and I cannot figure it out. I have not pinned delts since, because I like to be able to train upper body.