Toilet tank suddenly opened by itself and one of the toilet valve is extended beyond the toilet tank height. What should I do? Can I fix it by myself?
Looks like your fill valve extended.  They are adjustable in height, and there's usually a retaining ring or a screw mechanism to adjust the height.
I'd go buy a new fill valve kit at a hardware store.  you'll need to drain the bowl, unscrew the supply line from the fill valve and replace the fill valve in the toilet, but the instructions are generally provided in the kit.