There are a number of things that can cause this. First and foremost is the spark plug so we need to remove it and see what it looks like. Can you get a picture of it and let us know if it is fouled? Below is a chart that will help with this.
Here is a guide that will help with a misfire as well:
Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.