So my 6 month old got a cold from my 3 year old. He has a cough and runny nose and slightly warm but no high temperature

I also breastfeed him I don’t know if that matters

But I cannot see him in pain, but since he is 6 months I don’t know medicine is safe to give him and what I should give him.

And if I can give him medicine how many ML do I give him in the little syringe thing?

Hopefully someone can help