Need help my RIR limping now she has a red bump on leg

My RIR has been limping for a month now at the least. Thought she sprained her leg but it is just not healing. Now today I found a rather large red lump on her leg that is obviously hurting her and she is panting all the time. I am so confused on what to do. I put a piece of a wash cloth on her leg soaked with Veteriacine and taped it to her leg. Had luck with Veteriacine before at this point I am desperate to save my "Red" (thats her name). She is my nicest chicken and lays eggs very well. If any one has any suggestions that might help I am ALL EARS!!! SHe is only a year old, I have got to save my sweet girl! Please help!!