If you go to your boss, you better have some form of evidence that this colleague has indeed been avoiding you.  If you have been making all of your requests in person then that will be a problem for you as the colleague can easily play dumb if confronted by your boss.

The simple solution is to keep everything in writing.  If you need help from this colleague, send an email requesting help.  The colleague will either respond that they are too busy or won't respond.  In both cases, you have evidence that you can give to your boss should ask you what is preventing you from completing your tasks.