It’s broke, simple as that.
Shut water at valve underneath tank where water line is connected to.
Disconnect flapper ball from overflow tube tabs along with chain.
Take tank trip lever out of toilet. The nut on this is reverse thread and/or a pull clip.
Remove both of these items and take to a hardware store and replace with EXACT IDENTICAL PARTS.
Don’t listen to anyone that says, “Aww, this will work.”
It doesn’t work this way, too many different types of toilets and manufacturers to say this anymore.
Reinstall in reverse way you took them out. Should fix your issue with not a problem.
When you turn water back on to toilet, Make Sure You Tighten The Packing Nut Directly Behind The Handle.
A 1/8″ or 1/4″ turn is all you need to keep a leak from being created at the stem. The packing forms a memory over time around stem and lack of use will harden packing and cause it to let water past.