The light is warning you that there's a problem with the transmission.
Get the vehicle OBDII port scanned and check if there are any transmission error codes shown.
The error code number will indicate the type of problem with the transmission e.g. faulty sensor, gear solenoid etc.
A lot of major auto parts retail chains in the USA will scan the OBDII port for free.
Get it checked sooner than later before more problems are created.
Maybe also check the level of the transmission fluid to make sure that it is OK and also that the fluid looks OK (not dark and burnt looking) and doesn't need replacing etc.