Can i sue a neighbor for breaking HOA rules if the board does nothing?

There may be something specific to Illinois law that would change this response, and I do not practice in Illinois, so this response should not be considered specific legal advice and does not create an attorney-client relationship. Most HOA covenants provide that both the association and the individual members have the right to sue to enforce covenants. Particularly where the board has already made a determination that there is a violation, you should have a reasonable chance to sue to enforce the covenants. Boards often fail to sue to correct cited rules violations because they choose to spend the association's financial resources in a different manner. You probably have no way to force the association to take legal action, and it may be up to you. As a practical matter, talk to the board and find out why they have not further pursued the matter. If there are financial or other constraints that prevent them from going after the violation, and if you want to do so on your own, talk to the board about how you and the board can cooperate towards getting the situation corrected. The board can be a real ally in such situations.