Greetings, Bro. Marcos! Don't you know that the Russians issued each soldier a 2 ft length of 2x4 to beat the bolt open?
You have encountered the famous M-N Sticky Bolt Syndrome. It can be caused by a coupla things, but is SEEN in the M-N more than other rifles due to the small amount of leverage that the bolt HANDLE gives.
The most likely, and least serious cause, is a rough chamber. It MAY be rough from poor machining (hey- there was a WAR going on, for pity's sake!) but is most likely due to dried crud on the walls of the chamber.
An easy to try cheap fix- find a bore brush that is just a bit larger than the chamber. Make sure the rifle is unloaded. Remove bolt from rifle. Attach brush to a couple of section of cleaning rod with no handle. Chuck the rod into an electric drill. SWAB the chamber with a generous amount of your favorite bore cleaner (Hoppes #9 works fine) and let sit for 5 minutes. Slide the brush up into the chamber (not the bore, just the chamber) Hit the switch and spin the brush for 30-45 seconds. Remove, swab the bore with clean patches, and then repeat again.
The Soviets used a product similar to Cosmoline to preserve arms in long term storage (yours has probably been stored since WW II) and it is a bear to get off, since it can harden to the consistency of nail polish. In some cases, you may need to wrap the brush in a cotton patch, and apply a thin layer of toothpaste to it, and repeat the spin/clean cycle. Toothpaste contains a fine abrasive- it would take a hour of running to remove any significant amount of metal, and is safe to use. Now, there IS a product called J-B Bore Paste made to do the same thing, but if you don't HAVE a jar of it, and DO have some toothpaste........
And if you go over to surplusrifle.com, look up your rifle on the LEFT side, then look at the articles on the RIGHT side- you'll see one on sticky bolt. Also a good article on improving the HORRIBLE trigger pull many of these have.
With some luck, you can put away the rubber mallet.