Thank you for sharing your dream with us. Please take everything that I share to the Holy Spirit as He Alone gives the accurate interpretation.
God may have used you to literally/spiritually pray for that child given the context of what you described. There are many mysteries in the spiritual realm that we may not completely comprehend. God is not restricted by time and space. We humans are body, mind, and spirit. Our body and minds are asleep when we sleep but our spirits do not sleep.
In addition, God may also be showing you your calling and/or future direction for a career especially if you’ve been praying and seeking direction about this. I don’t know if you are in the health field. It may or not be literal sick children but could also include immature hurting people that need spiritual help.