Yes you can use it but probably not yet, it will need to rot down a lot more most likely. When it gets to a loose fibrous more dirt like substance, you can use. This may take a few years yet.
The reason why is
wood will cause a nitrogen deficiency until it breaks down, from which point it will swing back the other way. If you want to use it more quickly, spread it about as a mulch on perennial territory and nature will do the job.
If you want to speed up the rotting mix it with dirt, but that's a lot of work.
You did good not throwing it away, the worst thing you could do. Never throw out plant matter, its the gardens fuel, in any form.