The pion-mass dependence of the nucleon mass within the covariant SU (2) baryon chiral perturbation theory both without and with explicit ∆ (1232) degrees of freedom up to order p 4 is investigated. By fitting to a comprehensive set of lattice QCD data in 2 and 2+1 flavors from several collaborations, for pion masses Mπ < 420 MeV, we obtain low energy constants of natural size and compatible with pion nucleon scattering data. Our results are consistent with the rather linear pion-mass dependence showed by lattice QCD. In the 2 flavor case we have also performed simultaneous fits to nucleon mass and σπN data. As a result of our analysis, which encompasses the study of finite volume corrections and discretization effects, we report a value of σπN = 41(5)(4) MeV in the 2 flavor case and σπN = 52(3)(8) MeV for 2+1 flavors, where the inclusion of the ∆ (1232) resonance changes the results by around 9 MeV. In the 2 flavor case we are able to set independently the scale for lQCD data, given by a Sommer scale of r0 = 0.493(23) fm.