Many people have noted how big and scary The Mountain is from Game of Thrones. Unfortunately for UFC welterweight Gunnar Nelson, he found out the hard way just how scary he can be.

The Icelandic fighter grappled with him and was badly injured. The injury forced him to stay away from fighting in the UFC for years.

“I had a really bad injury that took a long time to recover from, I had two rib injuries back-to-back,” Nelson said on The MMA Hour via Pundit Arena. “I don’t know if you’ve had a rib injury but it’s horrible. It takes a long time and they can be so crippling.

“They’re just terrible it was at the top here so it affects the shoulder, affects the breathing, affects everything. I had two, on each side, but separate injuries.”

Gunnar Nelson had to deal with the first injury to his ribs. Then he had to deal with the second one that kept him out of the UFC for years.

“That’s what happened. It was two injuries, one of them that I’d had a while ago, actually, just before the [Gilbert] Burns fight. I went into that fight, fought that fight and recovered.

“Then, later, I got a probably even worse injury on the other side of my rib. Yeah, fuck it. You’ve probably seen the video of me and The Mountain rolling. This is where it happened actually.”

Gunnar Nelson detailed what exactly led to his injury. As it turns out Hafthor ‘The Mountain’ Bjornsson, doesn't even know what he did to the UFC fighter.

“I haven’t spoken to him about it. I don’t think he knows but I think this is the first time I’ve spoken about it. It happened there, it was fun, I enjoyed it but I wanted to get an armbar from the bottom.

“It was my mission because, obviously, it’s a hard thing against somebody like him and he knows a little bit. He knows how to use his weight a bit and he’s 160 kilos of pure muscle. ”

The UFC welterweight had no plans on stopping the grappling session once he got hurt. The submission would eventually present itself and that's when he would look to finish things.

“I catch him with an armbar from the top but I want to get it from the bottom and so I try to do that in the second round, he collapses on top of me and I could feel a nasty pop and seconds after.

“I could just feel it swelling up but something in me was like, I’m not going to say anything now, I’m just going to finish the round.

“It happens again where I get curled up like this and he pulls all his weight and at this stage, I’m just having real problems with my arm and breathing and stuff.

“I’m just thinking, ‘I have to wait for him to show his neck and we can get this over with’ because it’s too late to stop now and say that I hurt myself.”

“It was a really fun thing but it was probably stupid… I probably should have stopped when it happened.”

Gunnar Nelson is looking to make a return to the UFC. A fight should be announced soon as he looks to get back to the top.