I used too much thyme in my pasta sauce

Adding more tomatoes should balance it out.

Like PHIL said, if you have another can of tomatoes (or fresh) you can add that. I also think it will mellow after a day in the fridge; if not, adding fragrant olive oil and/or salt, then simmering, may also help round out the flavors.

Depends how much is too much but you can just add more tomatoes to dilute the thyme flavor. No sure what else you can do.