Can you please confirm the age of your baby.. at one year we give hepatitis a vaccine and not pentavac.
You can apply ice in the area, by covering it in a towel. Hardness will be there for two days. Redness could be due to the inflammation caused. If hardness is there for more than five days, along with fever, we will have to think of antibiotics and surgeon opinion for injection abscess.
Next Steps
For pain, you can give paracetamol drops.
Dose depends on the weight of the baby, so please do online consultation for that
Health Tips
If baby is not moving that leg like he moves other leg and there is warmth in the area, there is some inflammation there. try ice packs and drops for two days.