The second line is difficult and English versions vary considerably.
Quick answer
Indulge a servant from the beginning and the relationship ends up somewhere neither party planned. Exactly where is debated.
Read both lines
The first line is clear: מְפַנֵּק, pampering, from מִנֹּעַר, from youth. The second line's final word, מָנוֹן, occurs only here in the Hebrew Bible, which is why translations diverge so widely. The NKJV gives "as a son," others give heir, grief, weakling, or insolence.
This expression is debated and the catalog does not settle it. What every rendering preserves is the shape: something formed early produces an outcome late, and the outcome is not the one indulgence was aiming at. Read alongside 29:19, which said words alone will not correct a servant, the chapter has now bracketed both failures, too little engagement and too much accommodation, without prescribing the middle.
Related: Proverbs 29:19 · Proverbs 19:10 · Proverbs 30:21–23 · Proverbs 22:6
New King James Version®, Copyright © 1982, Thomas Nelson. All rights reserved. Full copyright information. Scripture provided by API.Bible.
Go Deeper
If this verse has been used to put weight on you that it was never carrying, ask about it directly.