The recent gravitational-wave detection GW250114 by the LIGO-Virgo-KAGRA (LVK) Collaboration provides unprecedented opportunities for precision tests of general relativity (GR) through black hole ringdown. In this study, we provide the first bounds on theory-agnostic deviations from the Teukolsky equation as described by the beyond-Teukolsky formalism. It directly connects deviations in the perturbation equations on the level of the effective potential in the Teukolsky equation with changes in the quasinormal mode (QNM) spectrum. We incorporate information on the final mass and spin from a full LVK inspiral-merger-ringdown analysis as parametrized priors in our analysis, reflecting theoretical uncertainties. Using publicly available LVK posterior information on agnostic damped sinusoid parameters, we then demonstrate how much beyond-Teukolsky potentials can be constrained. The high signal-to-noise ratio (SNR) allows us to avoid the expensive full Bayesian analysis of all parameters and to work directly with a simplified likelihood for the fundamental QNM only. This strategy is promising for future events with even higher SNR and allows, in principle, for a quick and simple test of GR without performing the full data analysis procedure, and provides a basis for complementary theory-specific tests. We report that current bounds on deviation parameters are in agreement with the Teukolsky equation.