Gap between bb an left crank arm
So I just purchased a new set of crank arms and attempted to install them. I have a square taper bb spindle, btw. So I installed the right side crank without any problems, but when it came time to install the left side crank arm it wouldn't slide all the way onto the spindle, leaving a gap between the crank and the bb as well as a portion of the spindle exposed. This doesn't look right at all I mean it definitely looks like all types of dirt and stuff can get in between, but I'm confused at how easily the other side went on. What are some possible problems and/or solutions.
Thanks in advance