Fisting is when part or all of the hand is put into the vagina or anus. This activity is not a high risk for HIV transmission which means HIV is not commonly passed this way.  HIV cannot be transmitted through cracked or dry cuticles.
The risk of HIV is increased with fisting if blood is present. Open bleeding cuts on your fingers or hands can allow access to your bloodstream. Friction from dry or rough penetration can cause vaginal and/or anal tearing in your partner. Transmission is more likely with shared rectal mucus and blood between multiple partners.
To reduce the chances of passing infections, wear a glove (a new one for each partner) and use plenty of water based lubricant with fresh, separate portions for each partner.  If fisting is new to you or your partner/date, start slow and check in with each other frequently to make sure that what is happening feels good to both of you. Keep your nails short to avoid injuring yourself or your partner and to prevent tearing of the glove.