Had the transmission flushed now the check engine light is on the light was not on before the car has 87000 miles

When did you first notice the light? Has been on since the work on the transmission?
If this is the case it's possible that the vehicle was started before all the electrical connections were reattached. It's also possible that a connection was forgotten or has came loose after the work. For example if you unplug the one of the fuel injector connection's and start the car it will give you the check engine light and generate an error code. That will stay active even after you plug the injector back in until the code is cleared.

This however is only an assumption due to the recent work. Any engine light and or code should be taken seriously until you can positively ascertain it's cause. Your recourse should be to retrieve the code and identify it's cause.
There are several ways you can do this. First is to retrieve the codes yourself. The steps for this are as follows.

• 1. Insert the ignition key into the ignition switch.
• 2. Turn the key 3 times to the on position with in 5 seconds. Do not turn it to the start position.

• 3. With pen and paper handy record what appears in the odometer window. An example of a code is P0302 or P1479.