No you shouldn't worry. C# is similar to C++, but in my opinion C# is a lot easier than C++ so you have a big advantage here. Also Java is close to C#.
When I took my degree we only learned C# and Java and I don't remember the big differences. I never read the C# book because it was kinda obvious and easier just to follow the documentation rather than the book since the logic is the same. There are a few things such as get and set, but that's something you can easily learn.
Now I'm only working on web technologies as this is where my interest has always been. If it makes you feel any better I have had both Windows and macOS and in both cases I run the whole development environment on a Linux VM. I think students who complete a degree without ever tried Linux have a problem rather than in your situation.
What's important from your degree, depending on where your focus is going to be, is something like general understanding of programming such as variable types, arrays, OOP, what sorting algorithms are and why it's good to know there are different types and most important how to understand the needs of the client and learn how to communicate with non-developers. The rest is something you can quickly pick up.
If you feel you have the time and interest, I see no problem in playing around with whatever technology you find most interesting, but as I said, that's not the most important thing. Some students finish their degree and having no real clue about programming, that's a problem.
A programmer should never end studying new possibilities :-)