Хва́стать — не коси́ть, спина́ не боли́т.
Literal: Bragging is unlike mowing; it won’t make your back ache.
A boaster and a liar are first cousins.
Disclaimer: It’s so disheartening when doing research to find what correlates with some the proverbs. In this one I had a choice between the top picture and bottom picture. I realized they both send a message, the first one deals with a backache. The other deals with an ache in the back. The reason for the disclaimer, well I’m not choosing what comes up at the head of the list, google is. Therefore I put it before my readers which is the better choice?