Mini Cooper - Engine light on - Is it alarming enough to return the car?

Hi! I have recently purchased a second-hand mini (with 30k miles on it). I have
driven it 50 miles or so. Within a week of purchasing it, out of the blue, I saw
an engine warning appear on my dashboard. As the first thing to do, I checked
whether the gas cap was loose. It wasn't. I am going to take the car to the
service of the place I purchased it from. But I am just wondering if you think
that this problem is alarming enough to return the car (I have a warranty and I
can return the car if I want to). I'll appreciate any advise you might have.