Welcome to AndroidCentral Hopefully we can get you sorted.
If you click the "App Draw" icon at the bottom of your home screen, you should see your apps being displayed there. Does the app show up there?
If not, try going into your Setting -> Apps, from there try find that app that's causing the problem. Click on it and you should see an option to un-install.
If you are really worried about it, try not to visit 'dodgy' websites or download apps outside of the Google Play store. You can always factory reset your device as a last resort. hope this helps.