My girlfriend has a large bump on her inner thigh in her private area, what could it be?

My girlfriend has a bump on her inner thigh down there. i havent seen it. but she says its very sore. here about five monthes ago she was taken advantage of while out drinkin with some work friends. she got scared she had something so went and got tested. main concern was HIV. the test came back negative. im aware that HIV can lie dormant for some time but if you showed the symptoms (such as this bump) at the time you were tested wouldnt it came back positive if the symptoms were that of HIV? i read some related articles on yahoo answers that had similer problems. they mentioned boils and ingrown hairs. she says she had it for some time but thought nothing of it as it was much smaller. now it has grown and worries her alot. please help?