Help with sigma lens' focusing ring!

hello!

I just bought my second sigma lens, a 17-50 for nikon cameras, and I didnt know it had a focus switch (AF/M). Unlike my other sigma, 10-20, which has manual override. (minor drawback of the 17-50, lens like that should have override!)

I tried to twist the focusing ring while the switch was set to AF and, although it was hard to do it, it could be moved.

Later I read on the manual that I shouldnt be doing that because it might damage the AF mechanism.

Do you guys think I somehow already screwed it? How can I test to see if everything is alright?