to think or talk a lot about something, especially something it would be better to forget
Example:
- So you made a mistake, but there's no need to dwell on it.
Extra examples:
- Her mind dwelled gloomily on the future.
- I don't want to dwell on this subject for too long.
- She had learnt never to dwell on what might have been.
- They had no time to dwell on present miseries.
to look at something for a long time