Used car I think of purchasing and they said check engine light is no problem

"Check engine" light indicates a diagnostic trouble code (DTC) has been set according to the on board diagnostics (OBD) system. The "oil life" indicator is something else. The oil life light can easily be reset, check any number of YT vids on how to do that. Do NOT trust a seller who tells you not to worry about the check engine light. A code reader can reveal the code, as taking it to a mechanic or even a parts store with a reader can. The codes can be relatively simple things or really major things.

Following up to above; if it was an easy fix, the dealer would have already fixed it. The fact they are still showing a car with a check engine light blinking indicates the problem may not be an easy one.

Thanks for the reassurance as I have a bad feeling over it and feel pressured that it will be no big issue. Excellent advice. Thanks