Hey there ., baby weight is upto age ! Weight should be 2 times of birth weight at 5 months and 3 times of birth weight at 1 year .. so at 8 months it is approximately okay !
About runny nose , you can put normal saline drops in both nostril every 4-6 hrly so that it is easy for him to breathe and about cetrizine drops , can be given thrice a day same dose !
Next Steps
Prevention from cold should be taken ,
Health Tips
Give warm food/fluids !