If this is your first offense, I doubt that you will get any 'jail time'.
As for possible punishment:
Texas Penal Code
"§ 22.01. Assault
(a) A person commits an offense if the person:
(1) intentionally, knowingly, or recklessly causes bodily injury to another, including the person's spouse;
(2) intentionally or knowingly threatens another with imminent bodily injury, including the person's spouse; or
(3) intentionally or knowingly causes physical contact with another when the person knows or should reasonably believe that the other will regard the contact as offensive or provocative.
(b) An offense under Subsection (a)(1) is a Class A misdemeanor, except that the offense is a felony of the third degree if the offense is committed against:
(1) a person the actor knows is a public servant while the public servant is lawfully discharging an official duty, or in retaliation or on account of an exercise of official power or performance of an official duty as a public servant; or
(2) a member of the defendant's family or household, if it is shown on the trial of the offense that the defendant has been previously convicted of an offense against a member of the defendant's family or household under this section.
(c) An offense under Subsection (a)(2) or (3) is a Class C misdemeanor, except that an offense under Subsection (a)(3) is a Class A misdemeanor if the offense was committed against an elderly individual or disabled individual, as those terms are defined by Section 22.04.
(d) For purposes of Subsection (b), the actor is presumed to have known the person assaulted was a public servant if the person was wearing a distinctive uniform or badge indicating the person's employment as a public servant."
Source:
http://www.capitol.state.tx.us/statutes/pe/pe0002200toc.html
So, based on the above, this would likely be a Class A misdemeanor.
"§ 12.21. Class A Misdemeanor
An individual adjudged guilty of a Class A misdemeanor shall be punished by:
(1) a fine not to exceed $4,000;
(2) confinement in jail for a term not to exceed one year; or
(3) both such fine and confinement."