I don't think there should be anything to worry. It must be because of the injection, which was given to you. At times these muscular injections do pain a lot. Ask your doc, if you can use cold ice cubes on that area. A small lump may have formed because of pain, which would go away soon. Infact, some medicines, such as neurobeon, netmycin, etc. pain a lot.
45 years Male Attorney
Diagnosed UC October 1989
Had two stage J Pouch Surgery Nov 2005; Take Down March 2006
Complications after surgery - Incisional Hernia and Ano Fistulas
"There are only two ways to live your life. One is as though nothing is a miracle. The other is as though everything is a miracle: Albert Einstein
"What you are aware of you are in control of; what you are not aware of is in control of you."