Problem applies to a question or difficulty calling for a solution or causing concern. Dealing with a moral or social problem: Has financial and emotional problems.
There are nine meanings listed in oed's entry for the noun problem, three of which are labelled obsolete. See ‘meaning & use’ for definitions, usage, and quotation evidence. Definition of problem noun in oxford advanced learner's dictionary.
A problem is a situation that is unsatisfactory and causes difficulties for people. A problem can be defined as a situation or an issue that needs to be resolved or dealt with.