Looks ok man, mostly because you used 4 colors, it looks awesome because of that, but his muscles looks strange, but I guess you should try it again, something a little bit more complex.

 It does look pretty good in my opinion, nice use of colors. The only problem/question I have is whether the light source was supposed to come from two sides, as the arms both have highlights on the outside of the arm, which I don't think would happen with just one. Other than that, it's a good piece. Nice work.

I was / am afraid that when i dither it it willget messy...

 Nice! No really, It is very good. The only thing  I might suggest for this one is that you might want to dither some. No dithering kind of makes it look... not realistic, if you know what I mean. I f you don't know what I mean look up the word "dithering" and/or "pixel art" on google. :)