Hello, sorry for the delay, The "check transmission" light comes on whenever there is a code stored for the transmission control system. If you haven't noticed the transmission slipping any, and the shifts are solid and the shift points are where they are normally and strong and not slipping on the shift, then likely everything is alright, It could be just a speed sensor code, or a Gear position fault, a lot of times the contacts in the gear position switch will overtime become dirty somewhat, so raking the gear stick back and forth from P to L about 10 times, can clean the contacts on the gear position switch.
What I would suggest if you have to drive it a good distance tomorrow is this, Stop by a local chain auto parts store, such as Advance Oreilly or Auto Zone, Ask them to borrow their scanner, Take it out and hook it to the OBD II port in your vehicle under the drivers side dash area. Turn on the scanner and read the DTC's , you will get a PO and then likely 4 numbers after that, Such as PO1717 or PO735, something along those lines, If it's just a gear position or speed sensor fault, I would clear it, see if it comes back, Depending on what code is stored, that will give you an idea of what is at fault and whether it is something internal or external.
If it is driving normally, and the shifts are strong and not slipping, I would say it is fine to drive, but if you notice any slippage or banging hard into gear, I may suggest getting it looked at by an Aamco transmission shop or at least a local tranny shop with good reviews. Let me know if you have any further questions. I try hard to provide 5 star service so don't hesitate to ask me anything else if you need to. Thank you.