BCG vaccine, although is given at birth, the local reaction begins appearing around 2-4 weeks and resolves completely by 2-4 months, leaving a small scar Around 4 weeks you can see a small red swelling at the site of injection, this will become like a small  blister by 6-8 weeks, after which the blister will burst and leave a healing ulcer which will become a small scar (around 3-5mm in diameter ) by the end of 3-4 months. This is perfectly normal progression of a BCG vaccine If this swelling is at the site where BCG vaccine was given at birth, there is nothing to worry about However if it is at an unusual site or if you suspect it could be something else, please consult your pediatrician for the same

Please elaborate on the site of the lump. A picture would be helpful. Does it hurt when touched, any overlying redness or pus discharge. Induration at the BCG vaccine site is a known occurrence but it would be valuable to know the time course. Better to consult directly.

Age of baby and photo lumb require to make diagnosis

Consult with Pediatrician physically for further evaluation and treatment