Had a pin jammed in upper knife now wont cut. Do I need to replace the knife?

It may be that the blades are not as sharp as they should be. You can improve the edge on a 5000 grit whetstone or just try another set of blades.

2pc Set Serger Knife Overlock Blade - Upper and Lower

Amazon.ca https://www.amazon.ca > ...

2pc Set Serger Knife Overlock Blade - Upper and Lower - Brother 925D 929D ... Return policy: Eligible for Return, Refund or Replacement within 30 days of ...

With lack of model number provided, Generic Videos below.

Without the knife in place once fabric is moving through the serger, it can easily drift too far into the moving upper and lower loopers. ... Solution: If the fabric edge is not to be cut, simply guide the fabric edge next to the cutting knife.
https://www.heirloomcreations.net/the-taming-of-the-serger/

If you mean that the needle has jammed with a build up of thread, then the only option is to cut the thread, raise the needle, if you can, and remove ALL pieces of cut thread. Sometimes if it's really jammed, you need to use a sharp knife, horizontally, to slice through the jammed thread.
The bobbin should be removed after this, and ALL traces of thread removed from all areas. Then, re-thread, re-insert bobbin, and try again.

Push it down with your finger.

Hi, yes I believe that will work, however you may need to re-adjust several time to get it perfect, my wife ( who's owned a couple industrial machines agrees ) use some scrap material to make adjustments and if possible ( with machine unplugged of course ) turn by hand to make sure it is not too far and could jam. I hope this was useful, please write back to let me know-even if not so we may try to help some more. Thanks for asking FixYa, and good luck-Prodzilla

if the knife is straight up and down it is in the cutting mode if it is pointing at you it is in the up mode,

you need to push it in and turn toward you at the same time to bring it straight up and down

mine is tuff and hard to do

If it won't cut then you need either a new upper knife or lower knife. One or both has gotten dull or nicked up. The place you got it serviced or any dealership should be able to order new knives for it.

It should just cut. Don't know too much about this machine as I'm new owner, but from what I can gather, either you need a new blade, or the upper knife is disengaged. The metal knob inside the threading area should be turned downwards, engaging the upper knife. The upper knife doesn't usually need replacing unless damaged, apparently. Hope this helps somewhat.

Call tech support! That's why these people get paid. Sites like this wouldn't need to exist if they did their jobs correctly!