Okay, if the water level is low enough in the bowl, and you have an old fasion plunger, you can try to quick plunge and see it the level dropes a bit. But before doing so. make sure to close the bathroom sink drain, and the tub/shower drain. Otherwise, the air you are forcing with the plunger will only escape through them.
If you do not have a plunger. Take a bucket, and fill it in the tub (or elsewhere) with hot water. Then if you have it, put a good amount of liquid dish shop (Dawn, Ivory, Joy...) directly in the commode, allow it to sit for 2 or 3 minutes, and then pour the hot water into it. It should be poured pretty quickly, but not so much as to overrun the bowl.
A word of caution... use only hot tap water, do not boil water and try this. The boiling water can break to porcelain.
If this resolves the blockage, you will notice it immediately. And rather than flushing the commode, repeat once more with the bucket full on hot water.
It will work, if it's a simple blockage. If it doesn't, then that indicates a more severe blockage.
