I was working on exoplanet spectral data from which I need to infer the concentration of gases. However, the exoplanet spectroscopy data contains only absorption wavelength and absorption radius. Is there any way with which I can derive the concentration of the elements in the exoplanet's atmosphere?
Sure, but it is not straightforward. There's a lot of degeneracies involved, such as many molecules sharing similar absorption bands, the presence of clouds, scattering, absorption happening at many different pressure ranges, solving the chemical equilibirum equations of the species and the temperature-profile modifying the overall spectrum as well.
There's a lot of "Forward" models available online, which "solve" for the atmosphere (Give you the theoretical spectrum) of a planet given for some initial conditions, such as metallicty, Carbon to oyxgen ratio, or concentration of molecules. What you want in your case is to do the inverse, i.e. start from your data and go to the mixing ratios of the different species. You can do that with "Retrieval" models, which you should again find information about online.
Assuming that you are working with transit data (which is what I understood from your post), you can often assume a constant temperature for the entire atmosphere at the equilibrium temperature of the planet, since transmission spectrum are usually less affected by the temperature profile, as they act more like passive absorbers.