My little (?) Lucy has colds from time to time and I let them clear up on their own, unless there are complications, i.e. eye trouble or excessive nose discomfort. Keeping them hydrated and rested and clean is important.

If you are really worried and Boomer seems to be going in the wrong direction healthwise, surely call the vet.

Colds are pretty common!

Get well Boomer! Hugs from Vermont cats..... and Sas ((((((((((((((((((((Boomer)))))))))))))))))))))))