If it was only imported a few days ago then it's probably still regenerating. I would give it a couple months (won't take that long) to see how/if it grows back. As long as it eats and can swim decently, worst case scenario is you name it Nemo
I have had a delhezi in this same situation b4 when I got it it was completely missing one fin including the arm part it was just a barely noticeable little stub ... The other side was missing the fin but still had the arm part ...... What happens is the side with the arm still completely intact grew the entire fin back normally after a few months ..... The side that was missing most of the arm part as well as the fin took much longer but it did grow back ..... But...... It resulted in a much smaller fin on that side about half the size or so as the other side .... Like dr. B stated in looked a bit like nemo and it swam funny for its entire life ..... But it did live and it did manage to warding and was healthy the 6-7 years I had it .... But it never grew back like it was supposed to ..... But the fish was completely fine ..... So in the case of my experience it will look funny forever but if u cut off the rest of the arm part it will either not grow back at all or it will be worse than b4 ..... I wouldn't do it just let grow back however it's going to ..... That's the best case scenario