"is there medication to help prevent the virus I can start taking Asap."
No
"How likely will I contract hep c"
Well since you just poked yourself with it I would compare it to a needle stick in the health care industry.
What is the risk for HCV infection from a needlestick exposure to HCV-contaminated blood?
After a needlestick or sharps exposure to HCV-positive blood, the risk of HCV infection is approximately 1.8% (range: 0%–10%).
http://www.cdc.gov/hepatitis/HCV/HCVfaq.htm#c5
If your worried, wait the proper amount of time and get tested.
How soon after exposure to HCV can anti-HCV be detected?
HCV infection can be detected by anti-HCV screening tests (enzyme immunoassay) 4–10 weeks after infection. Anti-HCV can be detected in >97% of persons by 6 months after exposure.
How soon after exposure to HCV can HCV RNA be detected by PCR?
HCV RNA appears in blood and can be detected as early as 2–3 weeks after infection.
http://www.cdc.gov/hepatitis/HCV/HCVfaq.htm#c5
From the earlier posts, it sounds like the CDC statistics show your likelihood of contracting Hep C to be very small (<2%), which is great. If you do decide to get tested in the timeframes shared above, here is some information on what to expect:
http://www.medhelp.org/hepatitis-c/articles/Diagnosing-Hepatitis-C/2273
IV drug use is the most common way Hep C is spread today (
http://www.medhelp.org/hepatitis-c/articles/What-Is-Hepatitis-C/2251), so hopefully you can take steps to move on from that habit.