Blisters from vaccine?

My 1 year old son just got his 12 month old shots. The made a big deal about the chicken box one but when over so quickly what the other two were that I forget. However the other two vaccines in both injection spots have caused something that looks like a blister that has now scabbed over. I noticed the holes of where the shots were get slightly bigger 2 days ago and then slightly bigger than that yesterday so I put and antibacterial on it. Is this normal or a cause for concern? He doesn’t seem to be in any pain and still is just has lively has he usually is, no fever, and it doesn’t seem to itch him. Should I take him to the doctors