make a mountain out of a molehill

to make a mountain out of a molehill (exaggerate the importance or seriousness of a problem) -- делать из мухи слона; сильно преувеличивать
turn molehills into mountains

Anthony accused me of turning molehills into mountains by telling other people about the quarrel we'd had.

see also
[делать из мухи слона]
[make a meal out of sth]