Do you have an allergy to anti-inflammatory painkillers?

A few months ago, I had a toothache and took an anti-inflammatory painkiller given by an acquaintance, but starting in the evening, red spots appeared all over my body and it itched.

The next day, I went to the internal medicine department, checked what I had eaten the day before, and was told it seemed to be an allergy to anti-inflammatory drugs, so I received a prescription and recovered.

And recently, I fell and received treatment and medication, but red spots started appearing and spreading on my legs and arms again.

I went back to my previous internal medicine doctor, and they told me to only take Tylenol from now on...ㅠㅠ

Why did I suddenly develop an allergy to the anti-inflammatory painkiller that I had never had before?

Will this disappear again?? I'm really worried ㅠㅠ