Welcome to the forum!
Could you describe your camera and how you use it? And post a picture of it? Otherwise it is hard to advise. And post the developed paper to give us an idea of what happened. Was it blurred or a sharp and round image of a hole?
For now it would be guessing, but it could be that:
- the pinhole is too large
- light is reflecting/bouncing inside the camera, thus blurring the image
- the photo paper was loaded backwards, thus exposing through the photo paper?
For the first problem, use the Pinhole Designer at http://www.pinhole.cz/en/pinholedesigner/ to calculate the right pinhole size.
For the second problem, paint the camera matt black on the inside of put a piece of black paper on the inside for eliminating reflections.
For the third problem, test again and mark the photo paper upfront so you know what side should face the pinhole.
"Have fun and catch that light beam!"
Bert from Holland