As long as the transmission in the car is shifting at least somewhat then yes you can drive the car with the bad transmission.
But just remember that if you continue to drive the car with the bad transmission that eventually the transmission will fail which would leave you stranded on the side of the road or in a parking lot or stranding in the street.
Your transmission could suddenly go out when driving down a busy highway which could lead to a deadly crash if someone crashes into you when your vehicle suddenly stops rolling down the highway due to the bad transmission.
If the car is an older car that is not worth much and you just drive it down less busy roads to and from work etc then it would be okay to drive the car with a bad transmission.
However if the car is worth the cost of a rebuilt transmission or new transmission then it would be best to get it fixed.
The more you drive your car with the bad transmission the worse it will get and eventually the bad transmission will completely fail on you.
First make sure the transmission fluid is not bad and it's full because bad or low transmission fluid can cause shifting problems with the transmission.
The transmission fluid and filter may need replaced and then the transmission may work properly then.