Of course there is a limit. The question is how high it is. For instance, at high enough CO2 concentrations, the greenhouse effect doesn’t get much stronger anymore. Also, the more CO2, the faster it dissapears by eroding rocks. That happens on a geological timescale, though.
If we did something to lower temperature, I’d be very worried about the CO2 concentration’s other effect: feeling like suffocating all the time.