The man went to the Temple, probably on the same day as his healing. He may have gone there to offer sacrifices for his recovery or just to see and enjoy the privileges which had not been his for 38 years.

“Thou art made whole” = the tense of the verb indicates that the healing was permanent.  Many of the supposed cures from the pool may not have lasted very long, but the healing Jesus gave would last forever.

“Sin no more” = “no longer go on sinning.”  Jesus points out in #John 9:3 that all sickness is not caused by sin, but He does not say that sickness is never caused by sin.  Jesus implies here that this man’s infirmity was a result of his sin and if he keeps on sinning, something worse may happen to him.  What could be worse than being paralyzed for 38 years?  Jesus may be talking about a result in the physical realm, but more likely of one in the hereafter.

John 9:3 “Neither this man nor his parents sinned,” said Jesus, “but this happened so that the work of God might be displayed in his life.