Remove noise on nonlinear signal
It looks like you are plotting a histogram, which is basically an estimate of a probability mass or probability density function. Maybe this is not correct. If your x-axis label is wrong, and this is truly a signal as a function of time, then what you are looking for is an estimation of the actual signal given additive noise. A simpler solution is a frequency-based low-pass filter. People can provide more answers if they know the nature of the signal in your graph.