It can. Especially if you don't have a sterile needle and your mom will eventually find out trust me all my friends did it themselves and either their parents found out because they got an infection or because they were just fixing their hair.
It probably would have a greater chance of getting infected if youdid it yourself. If your mom won't let you get it done wouldn't she be even more mad if you did it yourself? Just don't take a risk. Wait a few months and try asking her again, maybe she'll say it's okay.
Yea its not worth it to do it yourself...just wait until u can legally get it done without parental permission...if u still want it at that time.
I got my ear pierced a second time and it hurt for me. I would not recommend you do it by yourself if you do not have the right equipment.