Oh a subject I have had much experience!
I have had to do a LOT of patching to keep my sails till I can afford to get new ones.
My UV damaged mainsail did 20,000 nms!
Get some contact glue for industrial use, I have a litre can.
I prefer to use heavier sail cloth than the sail repair tape, but tape is fine.
Coat the area of the hole with contact glue working it into the fabric as much as you can.
Coat the sail tape (yep, over the sticky stuff).
Leave both to dry till its touch dry.
Apply patch to hole.
HOLD patch on with both hands squashing firmly together and recite some long passage learned as a child. If you can't remember one and are in an anchorage wait for three dinghys to go past... Don't wave to them.
When that side is dry you can do the other side
Never let a sailmaker try to rip your sail with his fingers. Because rip they will! And then tell you the sail needs replacing. No it doesn't. It just needs patching. It needs replacing when it shreds.
As to why you got it, though its a puncture hole it could be chafe but look carefully at the rigging too to make sure you don't have a strand of stay poking out.