A nondependent son normally does not qualify you to file Head of Household.
The IRS says in Pub 17 (pages 23-25):
"You may be able to file as head of household if you meet all of the following requirements.
1. You are unmarried or considered unmarried on the last day of the year. See Marital Status, earlier, and Considered Unmarried, later.
2. You paid more than half of the cost of keeping up a home for the year.
3. A qualifying person lived with you in the home for more than half the year (except for temporary absences, such as school). However, if the qualifying person is your dependent parent, he or she doesn't have to live with you. See Special rule for parent, later, under Qualifying Person."
If you look at Table 2-1 on page 25, you will see that a nondependent child is not a qualifying child for HOH purposes, unless he meets an unusual case (see all the fine print) - like you can't claim him because you are a dependent on someone else's return (footnote 3 on Table 2-1) or he is a qualifying child under the rules for divorced or separated parents (see footnote 2 for Table 2-1).
Read through Table 2-1 carefully to see if any of this applies.