You should not pierce yourself or a friend at home. PERIOD.
Mainly because it can pose serious health risks such as bloodborne pathogens such as Hepatitis B, Hepatitis C, Tetanus and HIV. Not to mention the risk of infection that comes with piercing the body with unsterile tools and jewelry.
Professional piercing studios use sterile disposable needles/cannulas that are specially adapted for piercing. These needles have a medically assured standard, which you cannot expect to get if you happen to get your hands on needles online.
You can never get your home environment clean enough to perform piercings without risks. A piercing studio has extremely high requirements to comply with from the Environment & Health, they use specific surface disinfectants, gloves, disposable needles, sterile instruments and the entire room is wiped with medical surface disinfection between customers.
It doesn't matter how many DIY videos you watch on Youtube & Tiktok, it doesn't matter how many piercings you already have, there are endless things that can go wrong if you do the piercing at home, it's an extremely unnecessary risk to expose yourself to, you only have one body, it's worth better than some home experiments!
Trained piercers know body anatomy and know what anatomical requirements need to be met for different piercings, they can advise you against different piercings that are not suitable for your body. They know how deep and where the piercing should be and all professional piercers know where blood vessels & veins go so they can avoid hitting them. All these factors are important for the performance of a safe piercing and for a gentle healing.