Raised Tat

I am slightly panicking. I only have one tattoo at the moment. I got it done 2 years ago and it's on my upper thigh, near my hip. I've taken care of it and it looks great. I was putting lotion on earlier and I noticed part of it is slightly raised up like a mosquito bite. It hasn't been itching and I haven't noticed it before, so I have no idea how long it's been there, but it definitely wasn't there the last time I checked. All posts I've read on the internet have been from people who've had their ink for a few days or so. I've had mine for 2 years! Does anyone know what's happening?