My 6month baby had eye infection so doctor did blood test nd told crp as 6.4 is that normal doctor suggested antibiotic injection for that!

Ocular infection: Do not know what the doctor actually diagnosed or was treating, but there are few "eye infections" in a 6 mos old that would need a single antibiotic injection. Hopefully this doctor is pediatrician. If not, go and have your baby seen be a pediatrician. The CRP is a very non-specific indicator of inflammation and is not generally an indicator, by itself, of a need for antibiotics.