I use a cream called e-45 but honestly I have had self injury scars for YEARS and one day they just go... so you can't really say for certian if it's there forever.
If its a red mark, use creams and lotions, also remember fluid counts, drink more water it will help your skin and in turn the scar.
If it's a white/silver mark. Unfortunately they can remain for longer, and this is usually the last healing stage. They can fade with time and care.
If it is a indentation, for lack of better word. I have a few of these from more severe scars, then yes unfortunately they may not heal further. If the skin has returned to its normal colour but you have a indention where you cut it may have finished healing. I have too many to count, like this on my wrist which were from 2014. I did get a tattoo which covered a few of them, which is an option.
Lastly, I have had many people in my life since and nobody has referenced the scars or noticed them. I always pull my hand away and panic someone will see them but nobody ever notices it's me who is aware of them.
Give it time 5 months isn't five years... I think up to a year is still good time for it to be healing.
Hope this helps.
Lastly, I'm 25 and I still struggle with self injury. It isn't something that goes away and the urges will always be there. I hope you're okay, and I hope that you are able to fight future urges and find alternative outlets.