Give it time and space, without distractions. If that does not work do take distractions, and from time to time ask yourself: could this help me? How could this apply to something, or help me with a trail of thoughts?

By thinking of other games and concepts I already have a few ideas I want to explore.

This is a matter of creativity. If you are/were not trained in that area (which you absolutely can change in the long term) you can also consider joining up in a team and contributing that way. Let someone else do the creativity and designing, and maybe contribute some ideas to an otherwise established concept or topic. Or none of the sort, but contribute in a more technical and practical way.

Not sure if you've come up with something yet but I can give some things that help me come up with stuff.

For one, think of the games that you like and what you like about them.  Then, try to see which of those things you want to (or can) emulate.  And then from there, put a twist on it.  Trying to come up with something out of the blue can be really tough so if you grab some things out of the air that you know you already like, it can make it a bit easier.  That being said, it can still be tough to come up with a 'good' idea.  But a good thing to keep in mind is a mediocre idea done really well is always better than a good idea done poorly, so if you come up with an idea that you like, but you feel you can do better it can be good to just get started and something really special might come to you later.