A lump at the injection site is rather common when Baytril is given to snakes. That lump is often caused simply by the body identifying the Baytril as a foreign substance and the body trying to keep the Baytril separated. Right after giving the injection lightly massage the injection site, as this will help distribute the Baytril into the tissue. That kind of lump can last anywhere from 24 hours to four days.
Scarring (necrotic tissue) ussually occurs with higher doses of Baytril, that could be avoided by diluting the Baytril with saline. If you are worried about the dosage/weight ratio possibly being on the high side, contact your vet and ask, if the Baytril should be diluted.
Best of luck!