Being hard could be an indication of a tumor or cyst, but if you think it could be a respiratory infection, then Tylan 50 injectable can be given at 1/2 ml for under 5 pounds, and 1 ml for over 5 punds twice a day for 3-5 days. Be sure to use some plain yogurt for probiotics during and after giving antibiotics. If you think it could be an abscess, then you could try to lance and squeeze it to see if there is pus or a solid core inside. Does it seem painful?