Welcome to MA!
The triangle with the explanation symbol is letting you know it has found a problem, in this case a light going bad. My wife's mini had a bad brake light but when I would check they all worked but it was going bad. I have posted a picture of the page that shows how to see what has caused the warning sign. Mini like BMW are very picky about power and lights, make sure you get the proper replacement light.
I would suggest a good code reader, one that reads BMW/MINI codes a generic one will not read all the codes. I have a Foxwell you can find them on Amazon. I believe Carly is one that works with a phone and bluetooth reader, not sure someone els here may know.
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