Hi Noah :)
I use a filter as well, adjustable albeit on a 1/4 setting of power. This causes minimal surface movement, but there is some.
Betta's don't love surface movement or current, but on the other hand some don't mind it. If it is causing difficulty for him to make or maintain his bubble nest, he may try harder or just abandon it.
To aid him, you could baffle the filter to reduce current and surface movement. See link: http://www.bettafish.com/showthread.php?t=30139
; this has many differentl DIY's for baffling different filters :D