If i have a fresh cut on my thigh tht bled and i took a bath am i at risk for gangrene? or any other infections?

Unlikely: The risk of infection depends on what types of bacteria might have been introduced and the degree of injury. A simple cut with a relatively clean object, rinsed out and keep clean is unlikely to get infected. In contrast, heavily contaminated cuts, or cuts with significant soft tissue injuries are at higher risk - in which case antibiotics may be needed. Make sure your tetanus shot is updated.

Bath water is dirty: Bath water is not clean water (from a wound perspective) as you sitting in it, as there are germs but they would be diluted by the amount of water present. You can potentially get an infection but unlikely. Treat the area with topical antibiotics ; dressings and have your pcp look at it. Till wound heals, it would be prudent to have showers and use protectant dressings.