How should I take this measure against me?
Try to find out if it's really a restriction. Maybe they have an automatic system that blocks websites if it notices anything odd (I listen to a lot of summer dance compilations who use a lot of half-nude women as a background picture on their videos, gave me some funny moments when some manager walked by). Ask the helpdesk why some websites don't work.
A couple of weeks ago, I lost internet connection at the end of a monday, on my workstation.
Next day, the connection was not back, so I had to contact helpdesk.
You might use youtube as a source of information (a lot of documentaries and tutorials on youtube). This might be your argument if they ask you which kind of websites you are talking about. Tell them that it happened after you lost the internet connection.
Checking with colleagues, everybody had access, Youtube included.
You can also give notice that others do have access to the websites.
If they tell you it got blocked because of the music videos, then tell them you didn't know it was prohibited. Explain to them that the music relaxes you and provides you with a better focus. Also apologize for the inconvenience. But only IF they truely blocked it. Ask them if they can unblock it for the reason I just described (source of information), but don't use it for music anymore (unless it isn't prohibited), that would be unprofessional.
I hope everything will work out well for you.