GaN nanowires are important building blocks for next-generation UV- and visible range optoelectronic devices whose performance can be boosted via strain engineering. This necessitates the investigation of physical phenomena in  nanowires induced by elastic strains. The present paper studies deformation-induced features of Raman spectrum in individual horizontal GaN nanowire, in which elastic strain was created with AFM probe. Two-dimensional mapping  of the Raman signal is carried out with submicron spatial resolution in two polarization configurations. The Raman modes shapes and intensities are analyzed with respect to strain level and polarization of excitation. Deformation potential constants of A1(TO) and E2H modes are estimated from strain-induced spectrum broadening.