my baby boy will turn 3 months on March 18 and?

on March 14 he will have his 1st shots and i was thinking if i can put on his leg patch ELMA...on the package says that it can be use for babies from 3 months and so is it okay if i put it on my baby since to his 3 months will be just 4 days before in his day of getting shot

ELMA is a patch which u put on child hand or leg 1 hour b4 shot and so child will not feel pain.