I am experiencing buttock pain on the surface because of a spot. and it's quite swollen. severe pain on the spot but the spot is like a mosquito bite?

Need to examine: It is not feasible to provide a meaningful opinion without examining you and your symptoms warrant evaluation by a physician. The lesion is not likely to be a mosquito bite, but could be a spider bite, or infection of a hair follicle. Try warm compresses for a day or so, if that does not help, it would be prudent to see a doctor.