odors from sink post large rain.- have septic tank

We just finished a three day downpour of heavy rains. I have recently moved here and I am a first time septic tank owner. Know very little about them. please help.also post third day of rain, we noticed a foul odor from the lower level, closest to the septic tank, sink in the smaller bathroom, No signs of debrie in the toilet, or sink just a foul odor. is it the septic system, or is it the trap in the sink has backed up? Please help as soon as possible I have poured hot water down the sink, the odor is better with the help of exhaust fans. But answers would be appreciated. thank you Mark.