Both are cattle medicines that are used off label in chickens. Tylan 200 is 4 times as concentrated as the 50, which cuts down on the volume, but it may be too strong. I would only give it orally, but I have given Tylan 50 injections without an issue. When giving intramuscular injections, it is always good to aspirate or pull back on the syringe for blood to make sure that you are not injecting into a vein. Also in chickens I would only inject 1/4 inch deep. Sorry about the swelling, and hopefully, it will return to normal.