Whether or not you clear all the errors is a good question, it really depends on you.
The most important thing is that you understand what the errors are and check that they apply to your design. Effectively, you need to sign them off so that you’re happy to have left uncleared design rule errors. There may be DRC errors that don’t apply to the methods you are using for manufacture or design, or that you may be happy to leave in. The point is that you must check them before sending the design off to the manufacturer, don’t ignore them.
There are some error markers which act as warnings more than errors, you must check each error flagged and decide whether it is relevant to you or not.
If you do decide that an error is 'acceptable' and can be retained, you can marked that error as an 'Accepted' error. This will serve as an indication from then on that you have considered this error and explicitly decided to accept it.
Don't simply delete errors that you want to accept, because running DRC next time will simply put the error markers back in (assuming the underlying error condition still exists).