More direct translations:
* Create a crisis out of a minor issue
* Exaggerate the problem
* Turn a small problem into a big one
Figurative expressions:
* Blow things out of proportion
* Overreact
* Make a fuss over nothing
* Sweat the small stuff
* Get worked up over nothing
* Panic over nothing
* Jump to conclusions
Proverbs:
* Don't sweat the small stuff.
* A stitch in time saves nine.
* Don't make a mountain out of a molehill.
The best phrase to use will depend on the specific context and the tone you want to convey.