Sometimes there is a prophetic word, instructions or a warning for others in a dream.
When it concerns someone else, the challenge is "how" and "when" to tell that individual, or even IF we should disclose what we know. These are a few things I've learned over the years:
Naturally we pray over this information
We wait to hear further instructions from the Lord
Holy Spirit may or may not speak further on the subject, if you do not hear anything else from the Lord, then likely it may not be the time or the season to disclose this to the individual. Our part is just to bathe that dream in prayer until its time.
It is also our responsibility to ask for the interpretation or what is the Lord specifically saying in this dream?. What good is it to tell a person a dream and neither you nor the person doesn't know what it means - that is unfruitful and can be frustrating
It is also good to note that you may not get the interpretation, that it may come from somewhere else. And on the flip side, the interpretation may also come in "pieces" as times goes by, little by little. I've had that to happen to me as well, a dream may come in one month and the interpretation 2 or 3 years later.
Remember TIMING and SEASON for the dream to manifest is in the HANDS of the LORD, not ours.
It is always wise to WAIT until we get the full meaning of what the Spirit of the Lord is saying - and not altar our lives on a "dream"
If it is life threatening, NO you do not wait - you let that individual know.