Hi. Today I Noticed Some Type Of Bite/sting On My

Hi. Today I noticed some type of bite/sting on my forearm but didn't think anything of it since Ive been bit before. Now I'm a bit worried because its pretty big & swollen. It doesn't itch. I dont see a bite or sting mark. It feels a little warm & a bit hard. It doesn't hurt either. Please tell me what you think..