You can install 0.10.3 by cloning the "devel" version from github. 0.10.2 is the last stable version (master on github).
Just follow the install instructions (using git) from this article: How I start Nim
If you git clone without specifying a branch you should get devel which is 0.10.3 at the moment.
git branch or git status will show you which one you have (active).
You can also git pull origin master and then switch with git checkout master and git checkout devel between the versions if you need to.
I cloned nim and installed 0.10.3. Running nim from the cmd tells me I am using 0.10.3. Still nimble install c2nim complains that I am not using that version?
What am I missing?
Actually it doesnt find any version!