Today he 3 months old with 38.5 temperature

Hi

Hope you can help me. .

First time that my baby with temperature,  38.5 sense evening. 

I not sure what to do.  He was happy before went to sleep not crying much. Nothing different but with temperature. .

Do I need to go to hospital, I'm breastfeeding,  tomorrow morning I will definitely go to see my GP. 

Please guide me and help. My second child 2.5 years also not well with runny nose, and choose. 

Thanks a lot!