Maybe a fungal problem brought on by excess watering. But it's really hard to see any detail at this distance. However, the lower leaves of peas often suffer - it doesn't really affect the crop. It would be useful to know where it is growing, geographically, that is.

UK on a sunny windowsill:) Should I maybe water less?, sorry about the picture quality

I had a hunch you might be over here, looking at the brickwork. If it is indoors on a windowsill in the UK it is almost certainly getting insufficient light. Is it in a conservatory? If so it will get more light than inside. And yes, I would suggest watering less. I'm not sure of your long term aims with this plant but it is less than optimal time of year to be growing peas. Plus a single pea plant would give you a couple of table spoons of peas max, even under perfect conditions.

BTW it's really important to state where you are on posts. So much in gardening depends on location.

Ok, thanks man :)

I planted it just to see if it would grow to be honest, but I do have a few more.

And what is it about the brickworck which makes it British? Hahaha