Was draining off the differential fluid and noticed a small piece of metal (~ quarter of an inch in length) on the drain plug.
Nothing strange felt in regard of the diff when driving the car before the drain.
Is it possible to identify which part in the diff this piece came off by just looking at this photo?
Should i just ignore it and go on without worrying much about this?

Any advice would be welcome, please.
thanks!

here is the chunk next to the drain plug.

 

Looks like the tip and flanks of a gear tooth - so yeah, maybe something to worry about. Normally the worst you'll find in a gearbox or diff, is metallic fuzz.

 

Looking at a 1-view 2-D photo, it's hard to exactly determine what it came off of. But I agree with billyboy - better to disassemble and find out/repair than to assume it's not serious.

Something like that could be the 1st clue about more serious issues about to surface. If you don't examine further and repair, there's a really good chance it'll bite you in the butt at the worst possible time. With my racecar experience I say it's a no-brainer to fix it now before it causes more expensive and disabling damage. You can likely drive the car gently until you have time to fix it, but don't put it off any longer than you absolutely have to.

 

thanks guys, I apricate the advice.

 

I found similar chunks attached to that drain plug once upon a time too.
Continued to drive the car for quite some time. Eventually replaced the diff with a good used one.
YMMV...