Chomsk is in Grodno Gubernia, I believe.
A little SE of Kartuz Bereza.

The BARG (Bereza Area Research Group
includes Chomsk in its research area.
Their website is

http://people.netscape.com/morse/barg

Although we don't have much on Chomsk
itself we do have much info on Bereza and
their are many Chomsky surnames listed.

Hope this helps.

Diane Jacobs
New York