What does this dream/nightmare mean?

It means you was sleeping.

You watch too many end of times movies.

To see the sun in your dream symbolizes peace of mind, enlightenment, tranquility, fortune, goodwill, and insight. It also represents radiant energy and divine power. Generally, the sun is a good omen, especially if the sun is shining in your dream. The sun may also be a metaphor for your "son".

To dream that the sun has a creepy, harsh glare represents a significant disruption or serious problem in your life. The sun is considered a life-giver and thus, any abnormalities and peculiarities to the sun's appearance represent some sort of pain or chaos occurring in your waking life.

To dream that the sun is exploding signifies a traumatic or devastating end to a situation or relationship. You feel that an important aspect of your life is over.

Scary dreams are meant to shake you up so that you can take an objective look at your life and make some new decisions that would move you in a direction of success and happiness. Your dream suggests that you are in a situation that is overwhelming your life and you feel that you are loosing control of your life. It could be related to your future (job, relationship, school, family situation, etc). Perhaps you feel you do not have control anymore and external forces are taking over. It's affecting many in the same way. You are seeing this dream so that you can realize what is happening in your psyche and in the psyche of others. You have the strength and courage to weather this and furthermore, the ability to guide and help others through a difficult time.

Actually, that is somewhat true. The sun goes through many phases in its lifetime. At the very end of the cycle, the sun will expand and basically "eat" or engulf the nearby planets; Mercury, Venus, Earth and Mars. But, this is BILLIONS OF YEARS from now. We will be long dead before this happens to us.

the funny thing is, the sun is actually getting hotter. the ozone layer is starting to go away which means its getting hotter. you have to prepare your body

I think it means people need to grow in love and dignity cause if they don't grow - they will end up dying from not measuring up to evolving expectations

This is a common dream.  It's the opposite of the story of Icarus who flew into the sun.   Human beings are afraid of fire, so the fear of the sun and perhaps the fires of hell came from that same nightmare.   

That will happen in a few billion years.

Peace.

Idk.  Perhaps you've been watching too many disaster movies. (Ecclesiastes 1:4) "A generation is going, and a generation is coming, But the earth remains forever."