About 3 min aqo my baby gold fish swam into the prpella of my internal filter and lost parts of its fin.

straigt after it swam to the bottom and looked sick and couldnt swim propably.

Is there anything i can do, im quite worried i will lose him.

it is still alive but is missing most of its tail fin so im not sure about it

has it lost most of his tail fin??

I had the same thing happen this week with my Pufferfish.
Mine didn't make it, but give him some time and good waterconditions, yours may pull through.
Fins will regenerate if the base of the spines is not effected.
How far is the damage?

And if possible, can you post a pic?

fins will grow back as long as the damage isnt down to the 'root'. Even with damage to the root fish can live happily as long as they can swim around. So as long as it isnt damaged so much so it cant swim around it will be fine.