There are couple of thread regarding same error but they are not active ,I think last they were active was around 1 yr back so I am opening the new thread .
If you want to run only your suite xml file, you need to select your suite file and select Run As-> TestNG Suite.
However, if you want to select a particular test and use the non test part of your suite file i.e. the suite/listeners/parameters section, then you can set this file as a template xml by going to Project Properties->TestNG -> Template XML File (give absolute path of your testng xml here)