Welcome to the forum!
When you say you're using the "pixelart style" do you mean that you're making tiny, 1 px squares to create the icons?
From your description, I think the problem is being caused by anti-aliasing, which is how Inkscape makes it's lines, and especially curves so crisp and smooth. (As far as I understand, almost all text that you see on the internet uses it too.)
If your drawing is nothing but tiny, 1px squares, then you can probably solve this problem by removing the anti-aliasing. In Document Properties > Page tab at the bottom, is a checkbox. If you can't see it (currently the dialog is so long, that many computer screens cover it up) you can bring it into view by at least temporarily docking the dialog.
To dock it, grab with the mouse, the bar just below the titlebar (it says "Document Properties" and it gives the key shortcut for calling up the dialog), and drag it towards the right side of the window. When it gets close, it will snap into place and you can release the mouse. Then you'll be able to scroll down and reach the anti-aliasing option.
If that does not seem to solve the problem, we'll need to look at your SVG file (or else we'll be doing a lot of guessing).
Edit
But note that if there is anything else in the file, besides the icons made of tiny, 1 px squares, the lack of anti-aliasing will probably be problematic.
